Activated carbon catalysts are widely used for different applications including heavy metal removals from gas and liquids. It has been found however that the performance of the activated carbon catalysts could still be enhanced.
U.S. Pat. No. 7,722,843 discloses a process for the removal of mercury from a combustion exhaust gas stream in a combustion exhaust gas purification scheme that includes a combustion exhaust scrubber system that uses an aqueous liquid to remove acid gases from the combustion exhaust gas. The process comprises providing a powdered mercury sorbent, introducing the powdered mercury sorbent into the aqueous liquid in the scrubber system, and after introduction of the mercury sorbent into the aqueous liquid, separating at least some of the mercury sorbent from the aqueous liquid.
The so-called Kombisorbon® process (Chemosphere Vol. 37 Nos 9-12, pp2327-2334, 1998 Elsevier Science Ltd) is a fixed bed process designed for the removal of heavy metals, in particular mercury and cadmium, dioxins and furans, other ecotoxic organic components from waste gases.
Typical raw gas conditions:
Gas temperatureup to 90° C.Dust2-10 mg/dscm (dry standard cubic meter)Mercuryup to 10 mg/dscmDioxin/Furan (TE)up to 300 ng/dscm
Clean gas criteria (new MACT emission standards for new FBIs (USEPA 2011, Federal Register: 40CFR Part 60): at 7% O2):
Mercury   <1 μg/dscmDioxin/Furan (TE)<0.004 ng/dscm
The Kombisorbon® system generally uses a conditioner and a fixed-bed adsorber. The conditioner includes a coalescer, a droplet separator and a heat exchanger to condition the flue gas to reach optimal parameters before entering the adsorber.
The Kombisorbon® process offers the following key advantages:                Removal of ionic mercury known as Hg2+ through adsorption as HgCl2 on the activated carbon        
Elemental mercury known as Hg0 by forming with the sulfur on the carbon mercuric sulfide known as HgS
Removal of dioxins and furans through absorption.
Typical applications are sewage sludge or hazardous waste incineration plants. The first commercial-scale Kombisorbon® unit was installed in a sewage sludge incineration plant in 1994. Since that time more than 20 units have been put into operation worldwide.